Table 1.
Masaoka Staging of Thymic Malignancies11 With Modifications by Koga et al12 and WHO Classification of Thymic Malignancies13
| Stage/Type | Definition |
|---|---|
| Stage | |
| I | Grossly and microscopically completely encapsulated |
| II (a) | Microscopic transcapsular invasion |
| II (b) | Macroscopic invasion into thymic or surrounding fatty tissue or grossly adherent to but not breaking through mediastinal pleura or pericardium |
| III | Macroscopic invasion of neighboring organs (ie, pericardium, great vessel, or lung) |
| IV (a) | Pleural or pericardial dissemination |
| IV (b) | Lymphatic or hematogenous metastasis |
| Histologic type | Description |
| A | Neoplastic oval or spindle cells; no atypia; no lymphocytes |
| AB | Type A with foci of lymphocytes |
| B1 | Plump epithelioid cells resembling normal thymic medulla |
| B2 | Scattered foci of atypical epithelial cells with lymphocytes |
| B3 | Round or polygonal epithelial cells with mild atypia with minor component of lymphocytes |
| Thymic carcinoma (C) | Histologic subtyping required |